Faecal matter in ice.

I remember being in Bombay (Outback 88) and we were told to wipe the top of the beer bottles before drinking them and don't have ice.

Sat in a small bar drinking a few beers and a lorry pulled up outside, next thing a massive block of ice was placed in the dirt outside. The barman went out side with his ice bucket and hacked away at the now dusty ice and filled his bucket up. The other cafes and bars came over and took their share too.
I've never drunk out of a beer bottle without first wiping the top, a tip from my illustrious father. This awaits those who don't: https://www.rospa.com/leisure-safety/water/advice/weils-disease/

Aye, In my teens I had similar advice from my equally illustrious father (of a family who were M&B employeer from the year dot).

That advice was reinforced by the not infrequent sight of stray (or at least unattended) dogs cocking hind legs over crates of bottled ale...

De rigueur, yet the sight of gash tats (ermm, worn by all 'genders') scuppering straight from a flash, silvered-bottle-neck brings a wee smirk to this face whilst I cringe inwardly.